Retardation plate and its manufacturing method, circularly polarizing plate and 1/2 wave plate using same, and a reflective liquid crystal display

ABSTRACT

A method is provided for manufacturing a wide band retardation plate which gives uniform phase difference characteristics to incident light over the whole visible wavelength region, and which, as it permits selection of raw materials regardless of whether they have a positive or negative intrinsic double refraction value, allows a wide selection of raw materials. For this purpose, the method comprises a machine direction-stretched film-forming step for transporting and stretching in an identical direction to the transport direction, a Material A of two or more materials having different positive intrinsic double refraction values to form a machine direction-stretched film, a transverse direction-stretched film-forming step for transporting and stretching in a perpendicular direction to the transport direction, a Material B of the aforesaid two or more materials to form a transverse direction-stretched film, and a lamination step for laminating the machine direction-stretched film and the transverse direction-stretched film.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a retardation plate and itsmanufacturing method, a circularly polarizing plate and ½ wave plateusing same, and a reflective liquid crystal display which can be used invarious fields such as personal computers, AV devices, portableinformation and telecommunications devices, games and simulationdevices, and a vehicle-mounted navigation system.

[0003] 2. Description of the Related Art

[0004] ¼ wave plates whose retardation (Re) is ¼ of wavelength are usedfor various applications, such as reflective liquid crystal displays,optical disk pickups and anti-fogging films. On the other hand, ½ waveplates whose retardation (Re) is ½ of wavelength also have various usessuch as in LCD projectors.

[0005] In these applications, it is desired that ¼ wave plates and ½wave plates manifest their full function with respect to incident lightin all visible wavelength regions. In this regard, examples of wide bandretardation plates which can fully demonstrate their functions withrespect to incident light in the visible wavelength region and formed bylaminating two sheets of polymer film having mutually different opticalanisotropy may be mentioned (e.g., Japanese Patent Application Laid-Open(JP-A) No. 05-27118, JP-A No. 05-100114, JP-A No. 10-68816 and JP-A No.10-90521).

[0006] However, in prior art laminated type retardation plates, twotypes of chips had to be formed by cutting a birefringence filmstretched in one direction, in directions subtending mutually differentangles with respect to the stretching direction, these chips then beingstuck together by an adhesive material and laminated. Moreover, when thetwo chips were stuck together, the coating of the adhesive material,cutting and sticking led to cost increases while decreased performancedue to angular offset when the chips were stuck together could not bedisregarded, hence improvements were desired.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide awide band retardation plate, in particular a wide band ¼ wave plate,wide band ½ wave plate and wide band circularly polarizing plate, whichcan be efficiently manufactured continuously at low cost by a simpleprocess, which can be continuously wound to permit easy storage, andwhich gives uniform phase difference characteristics to incident lightover the whole visible wavelength region, and to provide a reflectiveliquid crystal display having improved brightness using this retardationplate.

[0008] It is a further object of the present invention to provide amethod of manufacturing a wide band retardation plate which givesuniform phase difference characteristics to incident light over thewhole visible wavelength region efficiently, continuously and at lowcost by a simple process, and wherein, as raw materials having positiveor negative intrinsic double refraction values can be selected, permitsa large selection of raw materials.

[0009] The retardation plate of the present invention is a laminate oftwo or more materials having different intrinsic double refractionvalues, wherein, when the values of the retardation (Re) at wavelengthsof 450 nm, 550 nm and 650 nm respectively are Re(450), Re(550), andRe(650), Re(450)<Re(550)<Re(650). As a result, a wide band ¼ wave plate,wide band ½ wave plate and wide band circularly polarizing plate withuniform phase difference characteristics to incident light over thewhole visible wavelength region, and a high quality retardation platewhich may be used for a reflective liquid crystal display havingimproved brightness, can be obtained.

[0010] The retardation plate of the present invention is manufactured byone of the following aspects. The first aspect comprises a machinedirection-stretched film-forming step wherein a machinedirection-stretched film is formed by transporting, and stretching in anidentical direction to the transport direction, a material A of two ormore materials having different positive intrinsic double refractionvalues, a transverse direction-stretched film-forming step wherein atransverse direction-stretched film is formed by transporting, andstretching in a perpendicular direction to the transport direction, amaterial B of the two or more materials, and a lamination step whereinthe machine direction-stretched film and transverse direction-stretchedfilm are laminated. The second aspect comprises a machinedirection-stretched film-forming step wherein a machinedirection-stretched film is formed by transporting, and stretching in anidentical direction to the transport direction, a material C of two ormore materials having different negative intrinsic double refractionvalues, a transverse direction-stretched film-forming step wherein atransverse direction-stretched film is formed by transporting, andstretching in a perpendicular direction to the transport direction, amaterial D of the two or more materials, and a lamination step whereinthe machine direction-stretched film and transverse direction-stretchedfilm are laminated. The third aspect comprises an stretched film-formingstep wherein one of a machine direction-stretched film and a transversedirection-stretched film is formed by transporting, and stretching inone of an identical direction and a perpendicular direction to thetransport direction, two or more materials having positive and negativeintrinsic double refraction values, and a lamination step wherein thestretched films are laminated.

[0011] According to the methods of manufacturing a retardation plate ofthe first to the third aspects, a wide band retardation plate whichgives uniform phase difference characteristics to incident light overthe whole visible wavelength region can be efficiently and continuouslymanufactured at low cost by a simple production process, and as the rawmaterial can be selected regardless of whether the intrinsic doublerefraction value is positive or negative, a retardation plate can beefficiently manufactured with a large selection of raw materials.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a drawing specifically describing one example of the drylamination method.

[0013]FIG. 2 is a schematic drawing roughly describing one example ofthe retardation plate manufacturing method of the present invention.

[0014]FIG. 3 is a schematic drawing showing one embodiment of theretardation plate of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (Retardation Plate and Retardation Plate Manufacturing Method)

[0016] The retardation plate of the present invention is a laminate oftwo or more materials having different intrinsic double refractionvalues, wherein, if the values of the retardation (Re) at a wavelengthof 450 nm, 550 nm and 650 nm are respectively Re(450), Re(550) andRe(650), Re(450)<Re(550)<Re(650). In the retardation plate of thepresent invention, incident light is given phase differencecharacteristics due to layers wherein two or more materials having theaforesaid different intrinsic double refraction values, are laminated.

[0017] The retardation plate of the present invention comprises threeaspects, i.e., a first aspect wherein the two or more materials bothhave positive intrinsic double refraction values, a second aspectwherein the two or more materials both have negative intrinsic doublerefraction values, and a third aspect wherein the two or more materialshave positive and negative intrinsic double refraction values.

[0018] -Retardation Plate According to the First Aspect—

[0019] The retardation plate of the first aspect is an aspect whereintwo or more materials having positive intrinsic double refraction valuesare laminated. In the first aspect, it is preferred to arrange the slowaxis of each layer to be perpendicular by arranging the orientationdirections (orientation axes) of the molecular chains of each layer tointersect perpendicularly.

[0020] In the first aspect, when three or more materials having positiveintrinsic double refraction values are respectively laminated, to makethe orientation directions (orientation axes) or slow axes of themolecular chains in these layers intersect perpendicularly, byconsidering materials with a positive intrinsic double refraction valuehaving close values of Re(450)/Re(550) as one type of material, they maybe broadly divided into two materials depending on the value ofRe(450)/Re(550), and each layer of these two materials is laminated sothat the orientation directions (orientation axes) or slow axes of themolecular chains intersect perpendicularly.

[0021] In the aforesaid first aspect, by manufacturing the retardationplate in this way, the retardation expressed is a complex retardationwhich is the result of the characteristics of each layer canceling eachother out. In the retardation plate of the first aspect, two or morematerials all having positive intrinsic double refraction values arecombined, and by adjusting the stretching conditions such as thestretching direction and draw ratio, the wavelength dispersion of theretardation expressed is controlled, and Re/λ imparts substantiallyuniform phase difference characteristics to incident light over thewhole visible wavelength region.

[0022] <Materials of the First Aspect>

[0023] Examples of the material in the first aspect, in addition tomaterials having a positive intrinsic double refraction value(hereafter, referred to simply as “positive materials”), may alsocomprise other possible components as desired. This “material having apositive intrinsic double refraction value” means a material showing anoptically positive monoaxiality when the molecules are oriented in amonoaxial sequence.

[0024] For example, when the above positive material is a resin, itrefers to a resin wherein, when light is incident on a layer wherein themolecules have a monoaxial orientation, the refractive index of light inthe orientation direction is larger than the refractive index of lightin a direction perpendicular to the orientation direction.

[0025] Examples of the above positive material are resins, rod-shapedliquid crystals and rod-shaped liquid crystal polymers. These may beused alone, or two or more may be used together. In the presentinvention, of these materials, resins are preferred.

[0026] Examples of resins are olefin polymers (e.g., polyethylene,polypropylene, norbornene polymers, cycloolefin polymers), polyesterpolymers (e.g., polyethylene terephthalate, polybutylene terephthalate),polyarylene sulfide polymers (e.g., polyphenylene sulfide), polyvinylalcohol polymers, polycarbonate polymers, polyarylate polymers,cellulose ester polymers (whereof some have a negative intrinsic doublerefraction value), polyether sulfone polymers, polysulfone polymers,polyallyl sulfone polymers, polyvinyl polymers or multi-component(bipolymer, terpolymer) copolymers. These may be used alone, or two ormore may be used together.

[0027] In the present invention, of these, as the material used for thelayer having the lower (Re(450)/Re(550)) value, olefin polymers arepreferred, and of these olefin polymers, from the viewpoint of lighttransmittance characteristics, heat resisting properties, dimensionalstability and photoelasticity characteristics, norbornene polymers areparticularly preferred. Examples of the above olefin polymers are“ARTON” from JSR Corporation, “ZEONEX” and “ZEONOR” from Nippon ZeonCo., Ltd. and “APO” from Mitsui Chemicals, Inc.

[0028] The above norbornene polymers have a norbornene skeleton as arepeating unit. Specific examples are given in JP-A No. 62-252406, JP-ANo. 62-252407, JP-A No. 02-133413, JP-A No. 63-145324, JP-A No.63-264626, JP-A No. 01-240517, Japanese Patent Application Publication(JP-B) No. 57-8815, JP-A No. 05-39403, JP-A No. 05-43663, JP-A No.05-43834, JP-A No. 05-70655, JP-A No. 05-279554, JP-A No. 06-206985,JP-A No. 07-62028, JP-A No. 08-176411 and JP-A No. 09-241484, but arenot limited to these. One of these may be used alone, or two or more maybe used together.

[0029] Of these norbornene polymers, those with a repeating unitrepresented by any of the following structural formulae (I) to (IV) arepreferred.

[0030] In the aforesaid structural formulae (I) to (IV), A, B, C and Dare independent and represent a hydrogen atom or monovalent organicgroup.

[0031] Of these norbornene polymers, hydrated polymers from thehydration addition of polymers obtained by metathesis polymerization ofat least one type of compound represented by the following structuralformulae (V) and (VI) with a copolymerizable unsaturated cycliccompound, are preferred.

[0032] In the aforesaid structural formulae, A, B, C and D areindependent and represent a hydrogen atom or monovalent organic group.

[0033] The mass average molecular weight of the above norbornene polymeris preferably 5,000 to 1,000,000, but more preferably 8,000 to 200,000.

[0034] There is no particular limitation on the other components whichmay be contained in the material of the first aspect provided that theydo not interfere with the effect of the invention, and they may besuitably selected according to the purpose.

[0035] In addition, when the retardation plate (the retardation plate ofthe first to third aspects) of the present invention is used for anoptical application (e.g., display), the glass transition point when theaforesaid material (material having a positive or negative intrinsicdouble refraction value) is a resin, is preferably 110° C. or more, butmore preferably 120° C. or more.

[0036] <Composition of the Retardation Plate of the First Aspect>

[0037] The retardation plate of the first aspect comprises two or morematerials having different positive intrinsic double refraction valueslaminated together, as described above. In the first aspect, it is morepreferred to provide an adhesive layer which can make the layers adhere.The material of this adhesive layer is preferably one which does notaffect the wavelength dispersion of the expressed retardation, and inparticular, a material which does not affect the incident light in thewhole visible wavelength region.

[0038] The material of the above adhesive layer is preferably a materialwhich is compatible with the material of each layer. Specifically, whenthe resin having a positive intrinsic double refraction value is anorbornene polymer, the material of the adhesive layer is an adhesivecontaining an aliphatic ester polymer, aliphatic ester urethane polymer,aromatic ester polymer, aromatic ester urethane polymer or etherpolymer. These materials may be used alone, or two or more may be usedtogether.

[0039] The thickness of the retardation plate of the first aspect ispreferably 30 μm to 300 μm, but more preferably 50 μm to 250 μm. Thethickness of each layer is preferably 10 μm to 200 μm, but morepreferably 20 μm to 150 μm. The thickness of the adhesive layer ispreferably such that the product of the birefringence and thickness ofthis adhesive layer is smaller, specifically, 0.2 μm to 20 μm ispreferred, and 0.5 μm to 10 μm is more preferred.

[0040] <Method of Manufacturing the Retardation Plate of the FirstAspect>

[0041] In the methods of manufacturing the retardation plate of thepresent invention, according to the method of manufacturing theretardation plate of the first aspect, a machine direction-stretchedfilm is formed by transporting and stretching in an identical directionto the transport direction, a material A of two or more materials havingdifferent positive intrinsic double refraction values (machinedirection-stretched film-forming step), and a transversedirection-stretched film is formed by transporting, and stretching in aperpendicular direction to the transport direction, a material B of theaforesaid two or more materials (transverse direction-stretchedfilm-forming step).

[0042] “Material A” and “Material B” are materials having differentintrinsic double refraction values. In the method of manufacturing theretardation plate of the first aspect, when three or more materialshaving positive intrinsic double refraction values are laminated,materials having a positive intrinsic double refraction value areclassified into two types as materials having close values ofRe(450)/Re(550), and these materials are stretched as “Material A” and“Material B”.

[0043] The stretching method may be uniaxial stretching, or biaxialstretching for the purpose of controlling the thickness direction.

[0044] If biaxial stretching is performed, in the retardation plateobtained, the stretching is performed by orientating the molecularchains mainly in one of the longitudinal and transverse directions sothat the orientation axes in each layer intersect perpendicularly.

[0045] It is preferred that, after stretching, the formed machinedirection-stretched film and transverse direction-stretched film arelaminated (lamination step). In this lamination step, from the viewpointof efficiency and space saving, the stretched films are preferablytransported in the same direction and laminated together. The laminationis preferably performed by sticking the stretched films together, butmore preferably by sticking them together with the slow axes of thestretched films perpendicular to one another. By manufacturing theretardation plate in this way, a wideband retardation plate which givesuniform phase difference characteristics over the whole visiblewavelength region can be efficiently, continuously and economicallymanufactured by a simple process using raw materials having positiveintrinsic double refraction values.

[0046] There is no particular limitation on the sticking method, forexample, the films may be coated with an adhesive and stuck together,the films can be stuck together with an adhesive film sandwiched betweenthem, or they may be stuck together by the dry lamination method usingan adhesive.

[0047] The material of the adhesive or adhesive film is identical to theaforesaid material of the adhesive layer. The adhesive coating amount ispreferably of the order of 1 g/m² to 10 g/m² in terms of solid mass. Thethickness of the adhesive film is preferably of the order of 0.5 μm to10 μm.

[0048] In the dry lamination method, the adhesive is generally coateduniformly on the adhesive substrate and dried, and then pressed onto theother adhesive substrate under pressure. In this dry lamination method,it is preferred to leave some parts of both adhesive substrates whereadhesive is not coated so that adhesive does not adhere to the stickingrollers, and release of pressure between the rollers is automatic. Theadhesive used in this dry lamination method is preferably a urethaneresin, and preferably a two-solution type curing resin cured by mixingand reacting a main agent (OH group-containing compound) and curingagent (NCO group-containing compound). This adhesive may be dissolved ina solvent to make an adhesive solution, or it may be a non-solvent typeadhesive which does not use a solvent, but from the viewpoints ofenergy-saving, reduction of remaining solvent amount and fasterprocessing, the non-solvent type is preferred. If a solvent is used,this solvent is for example preferably toluol ethylene acetate or ethylacetate. In this case, the solids concentration in the adhesive solutionis preferably of the order of 20% by mass to 40% by mass. The pressureused for pressurization is preferably of the order of 1 kg/cm² to 50kg/cm². When a retardation plate is manufactured from a laminate ofthree or more layers by laminating three or more materials by the drylamination method, it is preferred to increase process efficiency bysticking the third layer on when two layers are stuck together andlaminated without providing a step for winding the laminate.

[0049] Here, an example of the dry lamination method will bespecifically described referring to FIG. 1. A dry lamination apparatus200 shown in FIG. 1 comprises a first stretched film supply means,second stretched film supply means, adhesive coating means, transportmeans, heating/ drying means, sticking means and rolling means.

[0050] The first stretched film supply means comprises a first filmdelivery apparatus 203 which supplies a first stretched film 208 a.

[0051] The second stretched film supply means comprises a second filmdelivery apparatus 204 which supplies a second stretched film 208 b.

[0052] The adhesive coating means comprises an adhesive housingapparatus 202 which accommodates adhesive, adhesive coating rollers 206a, 206 b, and a doctor blade 209. In this adhesive coating means, theadhesive coating roller 206 a is arranged so that its surface comes incontact with the aforesaid adhesive and first stretched film 208 a. Theadhesive coating roller 206 b is arranged so that its surface is incontact with the first stretched film 208 a. In this adhesive coatingmeans, the adhesive which was adhering to the surface of the adhesivecoating roller 206 a is scratched off and adjusted to a uniformthickness by the doctor blade 209 as the roller rotates in the directionof the arrow, and is uniformly coated on the first stretched film 208 a.

[0053] The transport means comprises a transport roller 207 a andtransport roller 207 b which transport the first stretched film 208 adue to rotation.

[0054] The heating/drying means comprises a heating/drying apparatus 201which can dry the adhesive applied to the first stretched film 208 a.

[0055] The sticking means comprises stick/nip rollers 210 a, 210 b whichcan stick the first stretched film 208 a and second stretched film 208 btogether.

[0056] In the dry lamination apparatus 200, first, the first stretchedfilm 208 a is supplied and transported in the direction of the arrowfrom the first film delivery apparatus 203 which rotates in thedirection of the arrow. When the first stretched film 208 a istransported between the adhesive rollers 206 a, 206 b in contact withthe rollers, the adhesive which was adhering to the surface of theadhesive roller 206 a is uniformly applied. Subsequently, it is furthertransported in the direction of the arrow above the transport roller 207a to the heating/drying apparatus 201. In the first stretched film 208 awhich was transported to the heating/drying apparatus 201, the adhesiveis uniformly applied to the surface and dried by heating. The firststretched film 208 a is then transported in the direction of the arrow,above the transport roller 207 b, and is transported to the stick/niprollers 210 a, 210 b. At the same time, the second stretched film 208 bis supplied from the second film delivery apparatus 204 which rotates inthe direction of the arrow, and is transported to the stick/nip rollers210 a, 210 b in the direction of the arrow. In the stick/nip rollers 210a and 210 b, the first stretched film 208 a and second stretched film208 b are stuck together by the bonding force in the nip part, and arethus laminated together to manufacture the retardation plate. Theretardation plate is then transported to a winding apparatus 205, andwound.

[0057] The aforesaid materials having a positive intrinsic doublerefraction value are as described above, and preferred materials are asdescribed above.

[0058] One embodiment of the method of manufacturing the retardationplate of the first aspect will now be described using FIG. 2.

[0059] An stretching/sticking apparatus 10 shown in FIG. 2 comprises amachine direction-stretched part 1, a sticking part 2 and a transversedirection-stretched part 3.

[0060] The machine direction-stretched part 1 comprises machinedirection-stretching low speed rollers 1 a, 1 b and machinedirection-stretching high speed rollers 1 c, 1 d.

[0061] The sticking part 2 comprises stick/nip rollers 2 a, 2 b andadhesive coating rollers 2 c, 2 d.

[0062] The transverse direction-stretched part 3 comprises a transportdirection adjustment roller 3 a and a transverse direction-stretchingapparatus 3 b.

[0063] In the stretching/sticking apparatus 10, the machinedirection-stretching low speed rollers 1 a and 1 b, the machinedirection-stretching high speed rollers 1 c and 1 d, stick/nip rollers 2a and 2 b, adhesive coating rollers 2 c and 2 d, and transport directionadjustment roller 3 a can respectively be rotated by a drive part, shownbelow. The machine direction-stretching low speed rollers 1 a, 1 b andthe machine direction-stretching high speed rollers 1 c, 1 d arearranged in this order from upstream to downstream. Heating means, shownbelow, are respectively installed around and inside the machinedirection-stretching low speed rollers 1 a, 1 b and machinedirection-stretching high speed rollers 1 c, 1 d, and control thestretching temperature of the stretched substrate.

[0064] In the stretching/sticking apparatus 10, the material Acomprising a resin having a positive intrinsic double refraction valueand the material B having a positive intrinsic double refraction valueare first transported in the direction of the arrow in FIG. 2 (transportdirection). Herein, the machine direction-stretching high speed roller 1c and machine direction-stretching high speed roller 1 d are set thatthey rotate at higher speed than the machine direction-stretching lowspeed roller 1 a and machine direction-stretching low speed roller 1 b.The machine direction-stretching low speed roller 1 a and machinedirection-stretching high speed roller 1 c are set so that they rotatein the opposite direction to the machine direction-stretching low speedroller 1 b and machine direction-stretching high speed roller 1 d(direction of the arrows shown in the figure).

[0065] The material A comprising a resin having a positive intrinsicdouble refraction value which was transported to the machinedirection-stretched part 1 in the stretching/sticking apparatus 10,comes in contact successively with the machine direction-stretching lowspeed rollers 1 a, 1 b and machine direction-stretching high speedrollers 1 c, 1 d, and while being transported in the transport directionshown in the figure, a tensile force is applied due to the rotationspeed difference between the machine direction-stretching low speedrollers 1 a, 1 b and machine direction-stretching high speed rollers 1c, 1 d, and the material is stretched in the transport direction(longitudinal direction of the film) due to this rotation speeddifference. At this time, temperature control can be performed by theaforesaid heating means while the material A is stretched, so thematerial A can easily be adjusted to suitable stretching conditionsdepending on the nature of the material and stretching speed (rollerspeed difference). After stretching, the material A comprising a resinhaving a positive intrinsic double refraction value is stuck to thematerial B comprising a resin having a positive intrinsic doublerefraction value in the sticking/nip rollers 2 a, 2 b which rotate inthe direction shown in the figure, and is then further transported inthe transport direction shown in the figure.

[0066] On the other hand, the material B comprising a resin having apositive intrinsic double refraction value passes beneath the transportdirection adjustment roller 3 a, and while being transported in thetransport direction shown in the figure, is transversedirection-stretched (tenter stretching) by the transversedirection-stretching apparatus (tenter stretching apparatus) 3 b in thetransverse direction-stretching unit 3. After an adhesive is coated bythe adhesive coating rollers 2 c, 2 d in the sticking part 2, it isstuck to the material B comprising a resin having a positive intrinsicdouble refraction via the adhesive in the sticking/nip rollers 2 c, 2 d,and transported in the transport direction shown in the figure.

[0067] In the stretching/sticking apparatus 10, by adjusting the drawratio and stretching temperature by the rotation speed of the rollersand heating means, the retardation plate of the first aspect having thetarget retardation can be efficiently manufactured.

[0068] There is no particular limitation on the heating means providedthat it can warm the stretching substrate to a suitable temperature. Anyheating means known in the art can be used, such as hot air, heatingrollers and infrared heaters such as near infrared heaters and farinfrared heaters. It is preferred that these heating means have anapparatus not only for heating but for controlling temperature. One ofmore of these heating means may be used alone, or two or more may beused together.

[0069] There is no particular limitation on the number of rollers in themachine direction-stretched part 1, which may be chosen according to thenature of the material of the stretching substrate and stretching speed,etc.

[0070] In the embodiment shown in FIG. 2, stretching of material Acomprising a resin having a positive intrinsic double refraction value,stretching of material B comprising a resin having a positive intrinsicdouble refraction value and sticking were performed continuously, butthe present invention is not limited thereto. For example, stretching ofmaterial A comprising a resin having a positive intrinsic doublerefraction value and stretching of material B comprising a resin havinga positive intrinsic double refraction value may be performedseparately. Alternatively, the stretching and sticking of the films maybe performed separately. These cases offer the advantage of space savingif the stretched films are temporarily wound.

[0071] In the aforesaid embodiments, if the dry lamination method isused as the adhesion method, a drying means to dry the adhesive ispreferably provided between the adhesive coating rollers 2 c, 2 d andthe stick/nip rollers 2 a, 2 b. There is no particular limitation onthis drying means, examples being drying means known in the art such asfor example warm air or a hot blast, or drying by dehumidification air.

[0072] There is no particular limitation on the stretching temperature,but if the minimum glass transition temperature of the basic material(material having a positive intrinsic double refraction value) in eachlayer is Tg(min), it is preferred to set it within the range(Tg(min)−30)° C. to (Tg(min)+30)° C.

[0073] In the method of manufacturing the retardation plate of the firstaspect, to efficiently laminate so that the stretching directionsintersect perpendicularly, stretching is performed so that the transportdirections of the stretched films coincide with each other and the slowaxes intersect perpendicularly, therefore steps such as chip cutting canbe omitted. In other words, as the retardation plate of the first aspectis a laminate of layers using two or more types of resin having positiveintrinsic double refraction values, by making the stretching directionsof each layer perpendicular, the slow axes of the laminate of two ormore layers can be arranged perpendicular to each other without fail.Hence, it is unnecessary to go through the delicate and complicatedangle matching during chip cutoff or chip sticking of the stretched filmwhich was required for manufacture of conventional laminated typeretardation plates, so retardation plates can now be efficiently andcontinuously manufactured by a simple production process. Moreover, asthe manufactured retardation plate can be continuously wound, storage isalso simple and easy.

[0074] Retardation Plate of the Second Aspect—

[0075] The retardation plate of the second aspect is an aspect whereintwo or more types of material having negative intrinsic doublerefraction values are laminated. In the second aspect, it is preferred,as in the retardation plate of the first aspect, that the slow axes ofthe layers intersect perpendicularly by making the orientationdirections (orientation axes) of the molecular chains in each layerintersect perpendicularly.

[0076] In the aforesaid second aspect, when three or more types ofmaterials having negative intrinsic double refraction values arelaminated, in order to make the orientation directions (orientationaxes) or slow axes of the molecular chains in these layers intersectperpendicularly, of these materials having a negative intrinsic doublerefraction value, materials having close values of Re(450)/Re(550) areconsidered as one material. Hence, the materials may be broadly dividedinto two types depending on the value of Re(450)/Re(550), and the layerspreferably laminated for each material so that in these two kinds ofmaterials, the orientation directions (orientation axes) or slow axes ofthe molecular chains intersect perpendicularly.

[0077] In the aforesaid second aspect, by manufacturing a retardationplate in this way, the expressed retardation is the retardation of acomposite body wherein the characteristics of each layer cancel eachother out. In the retardation plate of the second aspect, two or morematerials having different negative intrinsic double refraction valuesare stuck together, and by adjusting stretching conditions such as thestretching direction and draw ratio, the wavelength dispersion of theexpressed retardation is controlled, and Re/λ imparts substantiallyuniform phase difference characteristics to incident light over thewhole visible wavelength range.

[0078] <Material of the Second Aspect>

[0079] The materials in the second aspect, in addition to materialshaving a negative intrinsic double refraction value (hereafter, referredto simply as “negative materials”), may also comprise other possiblecomponents as desired. This “material having a negative intrinsic doublerefraction value” means a material showing an optically negativemonoaxiality when the molecules are oriented in a monoaxial sequence.

[0080] For example, when the above negative material is a resin, itrefers to a resin wherein, when light is incident on a layer wherein themolecules have a monoaxial orientation, the refractive index of light inthe orientation direction is smaller than the refractive index of lightin a direction perpendicular to the orientation direction.

[0081] Examples of the above negative material are resins, discoticliquid crystal and discotic liquid crystal polymers. These may be usedalone, or two or more may be used together. In the present invention, ofthese materials, resins are preferred.

[0082] The aforesaid resin may for example be polystyrene, a polystyrenepolymer (copolymer of styrene and/or a styrene derivative with othermonomers), polyacrylonitrile polymer, polymethylmethacrylate polymer,cellulose ester polymers (whereof some have positive intrinsic doublerefraction values), or multi-component (bipolymer, terpolymer)copolymerization polymers. These may be used alone, or two or more maybe used together.

[0083] The aforesaid polystyrene polymer is preferably at least onecopolymer of styrene and/or a styrene derivative, acrylonitrile, maleicanhydride, methyl methacrylate and butadiene. In the present invention,of these moieties, at least one selected from polystyrene, polystyrenepolymers, polyacrylonitrile polymers and polymethylmethacrylate polymersis preferred. Of these, from the viewpoint of high birefringence,polystyrene and polystyrene polymers are more preferred, and from theviewpoint of heat resistance, copolymers of styrene and/or a styrenederivative with maleic anhydride are particularly preferred.

[0084] <Composition of the Retardation Plate of the Second Aspect>

[0085] The composition of the retardation plate of the second aspect, asmentioned above, is a composition wherein two or more differentmaterials having different negative birefringence values are laminated.Also in the second aspect, as in the first aspect, an adhesive layerwhich sticks well to the other layers is preferably provided. Thematerial of this adhesive layer is identical to that of the firstaspect.

[0086] The thickness of the retardation plate, thickness of each layerand thickness of the adhesive layer are identical to those of the firstaspect.

[0087] <Method of Manufacturing the Retardation Plate of the SecondAspect>

[0088] Of the methods of manufacturing the retardation plate in thepresent invention, in the method of manufacturing the retardation plateaccording to the second aspect, a material C of two or more materialshaving a negative intrinsic double refraction value is transported andstretched in an identical direction to the transport direction to form amachine direction-stretched film (machine direction-stretchedfilm-forming step), and a material D of the aforesaid two or morematerials is transported and stretched in a direction perpendicular tothe transport direction to form a transverse direction-stretched film(transverse direction-stretched film-forming step),

[0089] The aforesaid “Material C” and “Material D” are materials forwhich the intrinsic double refraction values differ. In the method ofmanufacturing the retardation plate of the second aspect, when three ormore materials having positive intrinsic double refraction values arelaminated, the materials having a positive intrinsic double refractionvalue are classified into two types by materials having close values ofRe(450)/Re(550), and these materials are stretched as “Material C” and“Material D”.

[0090] In the method of manufacturing the retardation plate of thesecond aspect, the preferred stretching method and lamination step arecompletely identical to the retardation plate manufacturing method ofthe first aspect. When the material has a negative intrinsic doublerefraction value, as mentioned above, the preferred materials are asdescribed above.

[0091] The retardation plate of the second aspect, as in the method ofmanufacturing the retardation plate of the first aspect, may beefficiently manufactured for example by machine direction-stretching(longitudinally stretching) and transverse direction-stretchingmaterials having a negative intrinsic double refraction value using thestretching/sticking apparatus 10 schematically shown in FIG. 2 so thatthe slow axes of each layer intersect perpendicularly.

[0092] In the method of manufacturing the retardation plate of thesecond aspect, to efficiently laminate so that the stretching directionsintersect perpendicularly, stretching may be performed so that thetransport directions of the stretched films coincide with each other andthe stretching directions intersect perpendicularly, therefore stepssuch as chip cutting can be omitted. In other words, as the retardationplate of the second aspect is a laminate of layers using two or moretypes of resin having negative intrinsic double refraction values, bymaking the stretching directions of each layer perpendicular, the slowaxes of the laminate of two or more layers can be arranged perpendicularto each other without fail. Hence, it is unnecessary to go through thedelicate and complicated angle matching during chip cutoff or chipsticking of the stretched film which was required for manufacture ofconventional laminated type retardation plates, so retardation platescan now be efficiently and continuously manufactured by a simpleproduction process. Moreover, as the manufactured retardation plate canbe continuously wound, storage is also simple and easy.

[0093] Retardation Plate of the Third Aspect—

[0094] The aforesaid retardation plate of the third aspect is an aspectwherein two or more types of material having positive and negativeintrinsic double refraction values are laminated together. In the thirdaspect, it is preferred that the slow axes of the layers intersectperpendicularly by making the orientation directions (orientation axes)of the molecular chains in each layer parallel to each other.

[0095] In the aforesaid third aspect, by manufacturing a retardationplate in this way by adjusting stretching conditions, the expressedretardation is the retardation of a composite body wherein thecharacteristics of each layer cancel each other out. In the retardationplate of the third aspect, two or more materials having positive andnegative intrinsic double refraction values are stuck together, and byadjusting stretching conditions such as the stretching direction anddraw ratio, the wavelength dispersion of the expressed retardation iscontrolled, and Re/λ imparts substantially uniform phase differencecharacteristics to incident light over the whole visible wavelengthrange.

[0096] <Material of the Third Aspect>

[0097] The materials having a positive intrinsic double refraction valueand the materials having a negative value are as mentioned above.

[0098] <Composition of the Retardation Plate of the Third Aspect>

[0099] In the composition of the retardation plate of the third aspect,as mentioned above, two different materials having positive and negativeintrinsic double refraction values are laminated. Also in the thirdaspect, as in the first aspect above, it is preferred to provide anadhesive layer which makes each layer adhere well. The material of thisadhesive layer is identical to that of the first aspect above.

[0100] The thickness of the retardation plate, thickness of each layerand thickness of the adhesive layer in the third aspect are respectivelyidentical to those of the first aspect.

[0101] <Method of Manufacturing the Retardation Plate of the ThirdAspect>

[0102] Of the methods of manufacturing the retardation plate in thepresent invention, in the method of manufacturing the retardation plateof the third aspect, two or more materials having positive and negativeintrinsic double refraction values are transported, and stretched in anidentical direction or perpendicular direction to the transportdirection to form a machine direction-stretched film or a transversedirection-stretched film (stretched film-forming step).

[0103] Preferred aspects of the stretching method and lamination stepare completely identical to those of the first aspect. The materialshaving positive and negative intrinsic double refraction values arethose mentioned above, and preferred materials are also as mentionedabove.

[0104] In the method of manufacturing the retardation plate of the thirdaspect, to efficiently laminate so that the stretching directionsintersect perpendicularly, stretching is performed so that the transportdirections of the stretched films coincide with each other and the slowaxes intersect perpendicularly, therefore steps such as chip cutting canbe omitted. In other words, as the retardation plate of the third aspectis a laminate of layers using two or more types of resin having positiveand negative intrinsic double refraction values, by making thestretching direction of each stretched film parallel, the slow axes ofthe laminate of two or more layers can be made to intersect with eachother without fail. Hence, it is unnecessary to go through the delicateand complicated angle matching during chip cutoff or chip sticking ofthe stretched film which was required for manufacture of conventionallaminated type retardation plates, so retardation plates can now beefficiently and continuously manufactured by a simple productionprocess. Moreover, as the manufactured retardation plate can becontinuously wound, storage is also simple and easy.

[0105] -Physical Properties of the Retardation Plate of the PresentInvention—

[0106] As the photoelasticity of the retardation plate of the presentinvention, 20 Bluestar or less is preferred, 10 Bluestar or less is morepreferred, and 5 Bluestar or less is still more preferred. This is dueto the following reasons.

[0107] In general, when a retardation plate is used as a component of adisplay element, it is stuck to other components (e.g., polarizingplate). There is a bias in the stress when it is stuck, and a largerstress acts on the ends than at the center. As a result, a differencearises in the retardation so that the ends may appear whiter and displayproperties of the display element may be impaired. Therefore, if thephotoelasticity of the retardation plate is within the above numericallimits, even if there is a bias in the stress when it is stuck, thepartial difference arising in the retardation (Re) can be suppressedwhich is more useful in components such as display elements.

[0108] Preferred Combination of Materials in the Retardation Plate ofthe Present Invention—

[0109] In the retardation plate of the present invention, from theviewpoint of wavelength dispersion over the whole visible wavelengthregion, if the values of the retardation (Re) at wavelengths of 450 nm,550 nm and 650 nm are respectively Re(450), Re(550), Re(650), there isno particular limitation provided that Re(450)<Re(550)<Re(650) issatisfied, but it is more preferred that the following physicalproperties are also satisfied.

[0110] If the absolute value of the retardation (Re) at a wavelength of450 nm and a wavelength of 550 nm is respectively Re(450) and Re(550),from the viewpoint of obtaining a retardation where the characteristicsof each layer cancel each other out, it is more preferred that thelaminated layers include at least a combination of two layers whosedifference in the value of (Re(450)/Re(550)) is 0.03 or more. It isstill more preferred to include a combination of two layers whosedifference is 0.05 or more.

[0111] Further, if the absolute value of the retardation (Re) at awavelength of 450 nm and a wavelength of 550 nm is respectively Re(450)and Re(550), from the viewpoint of obtaining a retardation platesuitable as a ¼ wave plate and ½ wave plate, it is preferred that thelaminated layers include at least a combination of two layers for whichthe value of (Re(450)/Re(550)) differs, and that the value of Re(550) inthe layer having a smaller value of (Re(450)/Re(550)), is larger thanthe value of Re(550) in the layer having a larger value of(Re(450)/Re(550)).

[0112] There is no particular limitation on the positions of theaforesaid layer combinations in the retardation plate, and they may ormay not be in mutual contact in the vertical direction.

[0113] Regarding preferred combinations of the above materials, if thevalue of the retardation (Re) at a wavelength of 450 nm, 550 nm and 650nm is respectively Re(450), Re(550), Re(650), from the viewpoint ofeffectively satisfying Re(450)<Re(550)<Re(650), it is particularlypreferred to combine a material for which the wavelength dispersion ofthe characteristic refractive value is small as a resin having apositive or negative intrinsic double refraction value, and a materialfor which the wavelength dispersion of the characteristic refractivevalue is large as another resin having a positive or negative intrinsicdouble refraction value.

[0114] For example, if a norbornene polymer is used as the materialhaving a positive intrinsic double refraction value and a highretardation (Re), it is preferred that a material having a largewavelength dispersion of the intrinsic double refraction value is usedas the other material having a positive intrinsic double refractionvalue (material having a small retardation (Re). Specifically, if theintrinsic double refraction value (Δn) at a wavelength of 450 nm and awavelength of 550 nm is respectively Δn (450) and Δn (550), it ispreferred to select it from resins satisfying the following relation:

|Δn(450)/Δn(550)|≧1.02

[0115] It is more preferred to select it from resins satisfying thefollowing relation:

|Δn(450)/Δn(550)|≧1.05

[0116] It is preferred that the value of |Δn(450)/Δn(550)| is large, butin the case of a resin, it is generally 2.0 or less.

[0117] Examples of materials having a large value of the(Re(450)/Re(550)) are polyester polymers (e.g., polyethyleneterephthalate, polybutylene terephthalate), polyarylene sulfide polymers(e.g., polyphenylene sulfide), polycarbonate polymers, polyarylatepolymers, polyether sulfone polymers, polysulfone polymers, polyallylsulfone polymers and polyvinyl chloride polymers. Of these, polyesterpolymers polyarylene sulfide polymers and polyarylate polymers arepreferred.

[0118] Examples of materials having a small value of (Re(450)/Re(550))are olefin polymers and cycloolefin polymers (e.g., polyethylene,polypropylene, norbornene polymers), and cellulose ester polymers. Ofthese olefin polymers, norbornene polymers are particularly preferred.

[0119] In the retardation plate of the present invention, the aforesaidcharacteristic Re(450)<Re(550)<Re(650) can be satisfied by adjusting themass ratio, stretching temperature and draw ratio of the material usedfor each layer.

[0120] For example, in the first aspect of the retardation plate of thepresent invention, if a norbornene polymer, polyethylene terephthalateand polycarbonate are used as the material (resin) having a positiveintrinsic double refraction value, the short wavelength side largelyreduces the retardation, so Re(450)<Re(550)<Re(650) is obtained as aresult. By controlling the stretching temperature within the aforesaidlimits, and by making Re(λ)/λconstant over the whole visible lightwavelength region, a retardation plate exhibiting uniform phasedifference characteristics over a wide band is obtained. Further, byadjusting the draw ratio, wide band ¼ wave and ½ wave characteristicscan be obtained.

[0121] As mentioned above, the retardation plate of the presentinvention can impart uniform phase difference characteristics to lightover a wide band (visible wavelength region), and although it is alaminate, it can be manufactured efficiently and at low cost by a simpleproduction process. In the case of the retardation plate of the presentinvention, there is no need to take account of compatibility ofmaterials when selecting raw materials, and as it can be manufacturedwith any combination of materials, i.e., the intrinsic double refractionvalues can be all positive, all negative, or positive and negative, awide selection of materials is possible. It is also advantageous fromthe viewpoint of cost.

[0122] -Embodiment of Retardation Plate of the Present Invention—

[0123] An example of one embodiment of the retardation plate in thepresent invention is shown in FIG. 3.

[0124] A retardation plate 100 is a retardation plate of the aforesaidfirst aspect. A layer 101 comprising a resin having a positive intrinsicdouble refraction value, and a layer 102 comprising a resin having adifferent positive intrinsic double refraction value from this resin,are laminated together.

[0125] The layer 101 and layer 102 both have birefringence, and they arelaminated with their slow axes perpendicular to each other.Specifically, the orientation direction of the molecular chain in theresin having the positive intrinsic double refraction value contained inthe layer 101, is perpendicular to the orientation direction of themolecular chain in the resin having the positive intrinsic doublerefraction value contained in the layer 102. The retardation of theretardation plate 100 is the sum of the retardations in the layer 101and layer 102, so by laminating the layer 101 and layer 102 so thattheir slow axes are perpendicular, the retardation on the short waveside of the retardation plate 100 can be made small, and the retardationon the long wavelength side can be made large. As a result, theretardation Re(λ) and the ratio Re(λ)/λ at a wavelengthλof theretardation plate 100, can be made approximately constant over the wholevisible wavelength region.

[0126] In the above mentioned embodiment, a specific example was givenof a retardation plate comprising respectively one layer each of twotypes of resins having different positive intrinsic double refractionvalues, but the retardation plate of the present invention is notlimited thereto, and it may comprise three layers, four layers, or alaminate of three or more layers. By laminating three or more layers,the physical properties of the retardation plate are improved, so thisis preferred.

[0127] Applications of the Retardation Plate of the Present Invention—

[0128] By adjusting Re(λ)/λ, the retardation plate of the presentinvention can be used as a wide band ¼ wave plate as a display device invarious fields such as personal computers, AV equipment, portableinformation and telecommunications devices, games and simulation devicesor car navigation systems, and can be used in a reflective liquidcrystal display. Also, by adjusting Re(λ)/λ, the retardation plate ofthe present invention can be used as a wide band ½ wave plate in PBS forprojectors, etc.

[0129] When the retardation plate of the present invention is used as acircularly polarizing plate (λ/4 wave plate), over a wide wavelengthrange of 450 nm to 650 nm, it is preferred that, at least at wavelengthsof 450 nm, 550 nm and 650 nm, the value of (retardation (Re)/wavelength)is 0.2 to 0.3. It is more preferred that, at least at wavelengths of 450nm, 550 nm, and 650 nm, the value of (retardation (Re)/wavelength) is0.23 to 0.27. It is still more preferred that, at least at wavelengthsof 450 nm, 550 nm, and 650 nm, the value of (retardation (Re)/wavelength) is 0.24 to 0.26.

[0130] When the retardation plate of the present invention is used as aλ/2 plate, over a wide wavelength range of 450 nm to 650 nm, it ispreferred that, at least at wavelengths of 450 nm, 550 nm and 650 nm,the value of (retardation (Re)/wavelength) is 0.40 to 0.60. It is morepreferred that, at least at wavelengths of 450 nm, 550 nm, and 650 nm,the value of (retardation (Re)/wavelength) is 0.46 to 0.54, and stillmore preferred that it is 0.48 to 0.52.

[0131] According to the present invention described above, a wide bandretardation plate which imparts uniform phase difference characteristicsto incident light over the whole visible wavelength region, can beefficiently manufactured continuously at low cost by a simple productionprocess. Moreover, as the raw materials can be selected regardless ofwhether they have a positive or negative intrinsic double refractionvalue, a method of manufacturing retardation plates offering a wideselectivity of raw materials can be provided.

[0132] (Circularly Polarizing Plate and ½ Wave Plate)

[0133] Next, a circularly polarizing plate and ½ wave plate using theretardation plate of the present invention, will be described.

[0134] The circularly polarizing plate is obtained by laminating apolarizing plate and the aforesaid retardation plate of the presentinvention.

[0135] For the retardation plate, over a wide wavelength range of 450 nmto 650 nm, it is preferred that, at least at wavelengths of 450 nm, 550nm and 650 nm, the value of (retardation (Re)/wavelength) is 0.2 to 0.3,more preferred that at least at these three wavelengths, the value is0.23 to 0.27, and still more preferred that at least at these threewavelengths, the value is 0.24 to 0.26.

[0136] The ½ wave plate of the present invention is obtained bylaminating a polarizing plate and the aforesaid retardation plate of thepresent invention. For the retardation plate, over a wide wavelengthrange of 450 nm to 650 nm, it is preferred that, at least at wavelengthsof 450 nm, 550 nm and 650 nm, the value of (retardation (Re)/wavelength)is 0.40 to 0.60, more preferred that at least at these threewavelengths, the value is 0.46 to 0.54, and still more preferred that atleast at these three wavelengths, the value is 0.48 to 0.52.

[0137] Polarizing Plate—

[0138] There is no particular limitation on the aforesaid polarizingplate, and those in the art may conveniently be used such as for examplean iodine polarizing plate, a color polarizing plate using a dichromaticdye, or a polyene polarizing plate.

[0139] Of these polarizing plates, the iodine polarizing plate and thecolor polarizing plate can generally be manufactured by stretching apolyvinyl alcohol film, and adsorbing iodine or a dichromatic dye ontothis. In this case, the polarization axis of this polarizing plate is ina perpendicular direction to the stretching direction of the film.

[0140] The aforesaid polarizing plate may have a protective layer. Theprotective layer preferably comprises a material with a high opticalisotropy such as a cellulose ester, preferably triacetyl cellulose.

[0141] Laminate—

[0142] The polarizing plate and the retardation plate are laminated sothat the polarization transmission axis of this polarizing plate and theslow axis (the maximum refractive index direction) of this retardationplate, intersect. The angle of this intersection is preferably 30° to60°, more preferably 40° to 50° and still more preferably 43° to 47°.

[0143] -Applications—

[0144] The circularly polarizing plate of the present invention is ofsimple construction and is easy to manufacture. It functions as a wideband λ/4 wave plate, and can be used in various fields, in particularthe reflective liquid crystal display of the present invention mentionedlater. The λ/2 wave plate of the present invention functions as a wideband λ/2 wave plate, and can also be used in various fields, inparticular PBS for projectors.

[0145] (Reflective Liquid Crystal Display)

[0146] The reflective liquid crystal display of the present invention isformed by laminating a reflector, a liquid crystal cell and a polarizingplate together in this order. The retardation plate of the presentinvention is interposed between the reflector and the polarizing plate.

[0147] A preferred example of the construction of the reflective liquidcrystal display comprises a reflector, liquid crystal cell, theretardation plate of the present invention and a polarizing platelaminated in this order, or alternatively, a reflector, the retardationplate of the present invention, a liquid crystal cell and a polarizingplate laminated in this order.

[0148] The retardation plate may be a retardation plate having λ/4characteristics, the preferred numerical range for Re/λ being identicalto that of the retardation plate used for the circularly polarizingplate mentioned above. The reflective liquid crystal display of thepresent invention may also comprise other components if required.

[0149] In the aforesaid reflective liquid crystal display, when theretardation plate and the polarizing plate are laminated, the laminateis equivalent to the circularly polarizing plate of the presentinvention.

[0150] Reflector—

[0151] There is no particular limitation on the aforesaid reflector, andthose known in the art can be used.

[0152] The reflector is generally arranged on the outside of the reversetransparent substrate of the liquid crystal cell described later.

[0153] -Liquid Crystal Cell—

[0154] There is no particular limitation on the liquid crystal cell, andthose known in the art can be used, for example, a TN liquid crystallayer may be filled between the front transparent substrate and reversetransparent substrate. In this case, the inside of the front transparentsubstrate and inside of the reverse transparent substrate are formed ofan electrode layer comprising an electrically conducting film of ITO(indium stannic oxide). In the present invention, in addition to a TNliquid crystal layer, an STN liquid crystal layer may also be used.

[0155] The drive of the liquid crystal cell may be a matrix drive, ormay be a segment drive. In the case of a matrix drive, it may be asimple matrix drive or an active matrix drive.

[0156] Polarizing plate—

[0157] There is no particular limitation on the polarizing plate, andthose known in the art may be used.

[0158] In general, the polarizing plate is disposed on the outside ofthe front transparent substrate of the liquid crystal cell together withthe retardation plate of the present invention.

[0159] The aforesaid reflective liquid crystal display is for amonochrome display, but in the present invention, a color filter layermay be further disposed between the front transparent substrate and theretardation plate of the present invention. By forming a color filterlayer on the front transparent substrate, the display may also be usedas a color display.

[0160] The monochrome display functions of the reflective liquid crystaldisplay of the present invention will now be described.

[0161] When a voltage is not applied to the electrode layer (whitedisplay), if light is incident on the polarizing plate, this incidentlight will be plane polarized in the direction of the polarization axisby this polarizing plate. This plane polarized light is converted intocircularly polarized light by the retardation plate of the presentinvention, and this is incident on the liquid crystal cell. Due to theliquid crystalline molecule of the liquid crystal layer, this circularlypolarized light reaches the reflector as plane polarized light parallelto the polarization axis, and is reflected by the reflector so that itis again incident on the liquid crystal cell. Due to the liquid crystallayer, the incident plane polarized light becomes circularly polarizedlight. This passes through the retardation plate, is again convertedinto plane polarized light parallel to the polarization axis, passesthrough the polarizing plate, and becomes a white display.

[0162] Next, when a higher voltage than the liquid crystal saturationvoltage is applied to the electrode layer (black display), the planepolarized light which passed through the polarizing plate is convertedinto circularly polarized light by the retardation plate of the presentinvention. This circularly polarized light is reflected by the reflectorwithout change, passes through the liquid crystal cell without change,and then passes through the retardation plate of the present invention.In other words, the plane polarized light passes through the retardationplate of the present invention twice via the reflector until it reachesthe polarizing plate again, so the phase difference of the planepolarized light is shifted by 90°, and the reflected light from thisreflector does not pass through the polarizing plate so as to give ablack display.

[0163] In the reflective liquid crystal display of the presentinvention, the plane polarized light is converted into circularlypolarized light over practically the whole range of the visible spectrumby the wide band retardation plate of the present invention. As aresult, decrease of color and contrast due to the wavelength dispersionof the light incident on the liquid crystal cell, are mitigated, and ahigh contrast display is obtained.

[0164] Hereafter, some examples of the present invention will bedescribed, but the present invention is not limited to these examples.

EXAMPLE 1

[0165] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0166] First, a non-stretched polycarbonate film (Mitsubishi GasChemical Company, Inc., thickness: 100 μm) was transversedirection-stretched (tenter stretched) at a draw ratio of 1.1 and anstretching temperature of 135° C. so as to obtain a film having athickness of 92 μm. The retardation value (represented by Re(550)) at awavelength of 550 nm was 341.6 nm.

[0167] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and machinedirection-stretched at a draw ratio of 2.2 and an stretching temperatureof 130° C. so as to obtain a film having a retardation (Re(550)) of477.1 nm and thickness 60 μm.

[0168] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 155 μm was thus obtained. Thedrying means was the application of warm air (50° C., 0.2 m/s) aftercoating the adhesive but before sticking.

[0169] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=122.8 nm, Re(550)=145.7 nm and Re(650)=160.1 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0170] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

EXAMPLE 2

[0171] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0172] First, a non-stretched polycarbonate film (Mitsubishi GasChemical Company, Inc., thickness: 100 μm) was machinedirection-stretched at a draw ratio of 1.1 and an stretching temperatureof 140° C. so as to obtain a film having a thickness of 92 μm. Theretardation value (represented by Re(550)) at a wavelength of 550 nm was316.4 nm.

[0173] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.2 and anstretching temperature of 130° C. so as to obtain a film having aretardation (Re(550)) of 457.1 nm and thickness 45 μm.

[0174] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 142 μm was thus obtained.

[0175] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0176] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=121.1 nm, Re(550)=147.0 nm and Re(650)=160.3 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0177] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

EXAMPLE 3

[0178] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0179] First, polyethylene terephthalate was melt stretched at 290° C.by a T die, and cooling solidified on a casting drum at 30° C. tomanufacture a non-stretched polyethelene terephthalate film (thickness:45 μm). This non-stretched polyethylene terephthalate film was machinedirection-stretched at a draw ratio of 1.15 and an stretchingtemperature of 90° C. so as to obtain a film of thickness 40 μm. Theretardation (Re(550)) at a wavelength of 550 nm was 303.9 nm.

[0180] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.2 and anstretching temperature of 130° C. so as to obtain a film having aretardation (Re(550)) of 457.1 nm and thickness 45 μm.

[0181] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 90 μm was thus obtained.

[0182] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0183] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=124.4 nm, Re(550)=154.1 nm and Re(650)=165.1 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0184] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

EXAMPLE 4

[0185] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0186] First, polyethylene terephthalate was melt stretched at 290° C.by a T die, and cooling solidified on a casting drum at 30° C. tomanufacture a non-stretched polyethelene terephthalate film (thickness:400 μm). This non-stretched polyethylene terephthalate film was machinedirection-stretched (draw ratio=3.3) at an stretching temperature of 90°C., and then transverse direction-stretched (tenter stretching, drawratio=3.3) at 120° C. so as to obtain a biaxially stretched film ofthickness 40 μm. This biaxially stretched film was mainly oriented inthe machine direction (longitudinal direction), and the retardation(Re(550)) at a wavelength of 550 nm was 309.2 nm.

[0187] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.2 and anstretching temperature of 130° C. so as to obtain a film having aretardation (Re(550)) of 457.1 nm and thickness 45 μm.

[0188] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 90 μm was thus obtained.

[0189] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0190] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=120.3 nm, Re(550)=148.3 nm and Re(650)=162.8 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0191] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

[0192] From Example 4, it is seen that even when the film is stretchedand laminated biaxially, when the film is oriented mainly in the machine(longitudinal) direction or transverse direction, the same excellentproperties are obtained as when the film is stretched monoaxially in themachine (longitudinal) or transverse directions.

EXAMPLE 5

[0193] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0194] First, a non-stretched polycarbonate film (Mitsubishi GasChemical Company, Inc., thickness: 100 μm) was transversedirection-stretched (tenter stretched) at a draw ratio of 1.2 and anstretching temperature of 135° C. so as to obtain a film having athickness of 86 μm. The retardation value (represented by Re(550)) at awavelength of 550 nm was 634.1 nm.

[0195] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 200 μm) was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.2 and anstretching temperature of 130° C. so as to obtain a film having aretardation (Re(550)) of 915.4 nm and thickness 90 μm.

[0196] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 181 μm was thus obtained.

[0197] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0198] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=246.1 nm, Re(550)=280.8 nm and Re(650)=311.9 nm,respectively, and having wide band λ/2 wave plate characteristics.

[0199] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

COMPARATIVE EXAMPLE 1

[0200] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0201] First, a non-stretching polycarbonate film (Mitsubishi GasChemical Company, Inc., thickness: 100 μm) was machinedirection-stretched at a draw ratio of 1.1 and an stretching temperatureof 140° C. so as to obtain a film having a retardation (Re(550)) of316.4 nm and thickness 92 μm.

[0202] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and machinedirection-stretched at a draw ratio of 2.2 and an stretching temperatureof 130° C. so as to obtain a film having a retardation (Re(550)) of477.1 nm and thickness 60 μm.

[0203] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 155 μm was thus obtained.

[0204] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0205] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=817.1 nm, Re(550)=792.3 nm and Re(650)=777.1 nm,respectively, which are very high retardation values.

[0206] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

COMPARATIVE EXAMPLE 2

[0207] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0208] First, a non-stretched polycarbonate film (Mitsubishi GasChemical Company, Inc., thickness: 100 μm) was transversedirection-stretched (tenter stretched) at a draw ratio of 1.1 and anstretching temperature of 135° C. so as to obtain a film having aretardation (Re(550)) of 341.6 nm and thickness 92 μm.

[0209] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and machinedirection-stretched at a draw ratio of 2.2 and an stretching temperatureof 130° C. so as to obtain a film having a retardation (Re(550)) of457.1 nm and thickness 45 μm.

[0210] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 141 μm was thus obtained.

[0211] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0212] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=823.1 nm, Re(550)=798.3 nm and Re(650)=784.4 nm,respectively, which are very high retardation values.

[0213] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

COMPARATIVE EXAMPLE 3

[0214] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0215] First, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transverse direction-stretched (tenter stretched)at a draw ratio of 2.2 and an stretching temperature of 130° C. so as toobtain a film having a retardation (Re(550)) of 457.1 nm and thickness45 μm.

[0216] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and machinedirection-stretched at a draw ratio of 1.7 and an stretching temperatureof 130° C. so as to obtain a film having a retardation (Re(550)) of316.3 nm and thickness 73 μm.

[0217] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 123 μm was thus obtained.

[0218] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0219] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=143.9 nm, Re(550)=141.7 nm and Re(650)=140.8 nm,respectively. The values of the retardation (Re) satisfyRe(450)>Re(550)>Re(650), so the film was unsuitable as a wide band λ/4wave plate.

[0220] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

[0221] From Comparative Example 3, it is seen that the excellentcharacteristics of the embodiments are not obtained even if the sameresins are stretched and laminated in different directions.

EXAMPLE 6

[0222] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0223] First, a non-stretched polystyrene (thickness: 100 μm) wasmachine direction-stretched at a draw ratio of 2.1 and an stretchingtemperature of 105° C. so as to obtain a film of thickness 62 μm. Theretardation (Re(550)) at a wavelength of 550 nm was 453.2 nm.

[0224] Simultaneously, a polymethylene acrylate film (thickness: 100 μm)was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.4 and anstretching temperature of 110° C. so as to obtain a film of thickness 58μm. The retardation (Re(550)) at a wavelength of 550 nm was 602.8 nm.

[0225] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 123 μm was thus obtained.

[0226] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0227] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=121.3 nm, Re(550)=149.8 nm and Re(650)=169.7 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0228] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

EXAMPLE 7

[0229] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0230] First, a non-stretched polystyrene (thickness: 100 μm) wasmachine direction-stretched at a draw ratio of 2.0 and an stretchingtemperature of 110° C. so as to obtain a film of thickness 64 μm. Theretardation (Re(550)) at a wavelength of 550 nm was 339.9 nm.

[0231] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and machinedirection-stretched at a draw ratio of 2.2 and an stretching temperatureof 130° C. so as to obtain a film of thickness 60 μm. The retardation(Re(550)) at a wavelength of 550 nm was 477.1 nm.

[0232] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 128 μm was thus obtained.

[0233] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0234] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=121.3 nm, Re(550)=142.6 nm and Re(650)=154.2 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0235] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively.

EXAMPLE 8

[0236] A laminated film was manufactured as follows using thestretching/sticking apparatus 10 shown in FIG. 2.

[0237] First, a non-stretched polystyrene (thickness: 100 μm) wastransverse direction-stretched at a draw ratio of 2.1 and an stretchingtemperature of 110° C. so as to obtain a film of thickness 49 μm. Theretardation (Re(550)) at a wavelength of 550 nm was 305.9 nm.

[0238] Simultaneously, a norbornene film (Nippon Zeon Co., Ltd., ZEONOR:thickness: 100 μm) was transported in the same direction, and transversedirection-stretched (tenter stretched) at a draw ratio of 2.2 and anstretching temperature of 130° C. so as to obtain a film of thickness 45μm. The retardation (Re(550)) at a wavelength of 550 nm was 457.1 nm.

[0239] Next, the two kinds of film were stuck together using an adhesive(Dainippon Ink & Chemicals Inc., DICDRY, 5 g/m²) in the longitudinaldirection (film transport direction) by the dry lamination method, and alaminated film having a thickness of 98 μm was thus obtained.

[0240] The drying means was the application of warm air (50° C., 0.2m/s) after coating the adhesive but before sticking.

[0241] A film was thereby obtained for which the absolute valuesRe(450), Re(550) and Re(650) of the retardation (Re) at 450 nm, 550 nmand 650 nm were Re(450)=133.3 nm, Re(550)=149.8 nm and Re(650)=165.2 nm,respectively, and having wide band λ/4 wave plate characteristics.

[0242] The retardation (Re) of each sample at Re(450), Re(550), Re(650)and Re(750), and the value of Re(450)/Re(550), are shown in Table 1,respectively. TABLE 1 Examples/ Comparative Measurement wavelength (nm)Examples Sample 450 nm 550 nm 650 nm 750 nm Re(450)/Re(550) λ/4 idealvalue 112.5 137.5 162.5 187.3 0.818 Example 1 Polycarbonate 362.2 341.6328.5 320.4 1.066 (92 μm) Norbornene 481.1 477.1 476.8 475.0 1.008Laminate 122.8 145.7 160.1 166.5 0.823 Comp. Ex. 1 Polycarbonate 337.2316.4 301.7 295.4 1.066 (92 μm) Norbornene 481.1 477.1 476.8 475.0 1.008Laminate 817.1 792.3 777.1 770.2 1.027 Example 2 Polycarbonate 337.2316.4 301.7 295.4 1.066 (92 μm) Norbornene 461.1 457.1 456.8 455.0 1.009Laminate 121.1 147.0 160.3 167.7 0.823 Comp. Ex. 2 Polycarbonate 362.2341.6 328.5 320.4 1.066 (92 μm) Norbomene 461.1 457.1 456.8 455.0 1.009Laminate 823.1 798.3 784.4 775.7 1.030 Example 3 Norbornene 461.1 457.1456.8 455.0 1.009 Polyethylene 336.8 303.9 287.9 277.4 1.102terephthalate (40 μm) Laminate 124.4 154.1 165.1 178.4 0.807 Comp. Ex. 3Norbornene 461.1 457.1 456.8 455.0 1.009 Norbornene 316.4 316.3 316.6316.7 1.000 Laminate 143.9 141.7 140.8 139.8 1.016 Example 4Polyethylene 340.8 309.2 293.1 282.2 1.102 terephthalate Norbomene 461.1457.1 456.8 455.0 1.009 Laminate 120.3 148.3 162.8 173.4 0.809 Example 5Polycarbonate 675.1 634.1 602.9 590.3 1.065 Norbornene 922.4 915.4 913.3909.9 1.008 Laminate 246.1 280.8 311.9 320.8 0.876 Example 6 Polystyrene481.3 453.2 430.8 411.3 1.062 Polymethylene 603.5 602.8 600.8 599.31.001 acrylate Laminate 121.3 149.8 169.7 181.3 0.810 Example 7Polystyrene 360.9 339.9 323.1 308.4 1.062 Norbornene 481.1 477.1 476.8475.0 1.008 Laminate 121.3 142.6 154.2 166.3 0.787 Example 8 Polystyrene324.8 305.9 290.7 277.2 1.062 Norbornene 461.1 457.1 456.8 455.0 1.009Laminate 133.3 149.8 165.2 175.8 0.889

EXAMPLE 9

[0243] Circularly Polarizing Plate

[0244] The film obtained in Example 1 was used as a retardation plate.The retardation plate and a polarizing plate were adhered together sothat a slow axis of the retardation plate and a transmission axis of thepolarizing plate form an angle of 45° and thus an adhered plate wasmade. Then, the wavelength dispersion of Re values of this adhered platewas measured using a retardation measurement system (Oji ScientificInstruments, KOBRA21DH).

[0245] According to the results, Re/wavelength values of the adheredplate were about 0.25 throughout the entire visible light region, andthe adhered plate was a circularly polarizing plate showing ¼ wavelengthretarding property in a wide range. In addition, the adhered plateexhibited substantially the same Re values at the center and near theedge, and no whitening was observed at the edge.

EXAMPLE 10

[0246] Reflective Liquid Crystal Display

[0247] A Game Boy Color (Nintendo) video game was disassembled and apolarizing plate and a retardation plate mounted on the side facing theobserver were replaced with the circular polarizing plate of Example 9.Thus a reflective liquid crystal display (reflective LCD) was prepared.

[0248] The reflective LCD was able to display a sharp white image, whichwas uniform and sharp at the entire region of the display, from thecenter to the edge.

[0249] The present invention, which resolves the problems inherent inthe prior art, provides a wide band retardation plate which can bemanufactured efficiently and continuously at low cost by a simpleprocess. As continuous winding is possible, storage is also simple andeasy. The plate imparts uniform phase difference characteristics toincident light over the whole visible wavelength spectrum. Inparticular, it provides a wide band ¼ wave plate, wide band ½ wave plateand wide band circularly polarizing plate, and a reflective liquidcrystal display having improved brightness using this retardation plate.

[0250] The present invention further provides a method of manufacturinga wide band retardation plate which imparts uniform phase differencecharacteristics to incident light over the whole visible wavelengthregion efficiently, continuously and at low cost by a simple process. Asthe method permits selection of raw materials regardless of whether theyhave a positive or negative intrinsic double refraction value, theretardation plate can be manufactured with a large selectivity of rawmaterials.

What is claimed is:
 1. A retardation plate comprising: a laminate of twoor more materials having different intrinsic double refraction values,wherein the retardation plate satisfies the relation:Re(450)<Re(550)<Re(650), where Re(450), Re(550) and Re(650) areretardation values in wavelengths 450 nm, 550 nm and 650 nm,respectively.
 2. A retardation plate according to claim 1, wherein theintrinsic double refraction values of two or more materials arepositive, and the slow axes of each layer are mutually perpendicular. 3.A retardation plate according to claim 1, wherein the intrinsic doublerefraction values of two or more materials are negative, and the slowaxes of each layer are mutually perpendicular.
 4. A retardation plateaccording to claim 1, wherein the intrinsic double refraction values oftwo or more materials are positive and negative, and the slow axes ofeach layer are mutually perpendicular.
 5. A retardation plate accordingto claim 1, wherein the orientation axes of the molecular chains in eachlayer are mutually perpendicular.
 6. A retardation plate according toclaim 1, wherein the orientation axes of the molecular chains in eachlayer are mutually parallel.
 7. A retardation plate according to claim1, wherein the retardation plate further comprises an adhesive layer. 8.A retardation plate according to claim 1, wherein at least one of thematerials in each layer is a norbornene polymer.
 9. A retardation plateaccording to claim 1, wherein at least one of the materials is selectedfrom at least one of a polyester polymer, polyarylene sulfide polymer,polyarylate polymer and polycarbonate polymer.
 10. A retardation plateaccording to claim 1, comprising two layers wherein, when the absolutevalues of the retardation (Re) at a wavelength of 450 nm and awavelength of 550 nm are respectively Re(450) and Re(550), thedifference in the value of Re(450)/Re(550) of each layer is 0.03 ormore.
 11. A retardation plate according to claim 1, comprising twolayers wherein, when the absolute value of the retardation (Re) at awavelength of 450 nm and a wavelength of 550 nm are respectively Re(450)and Re(550), the value of Re(450)/Re(550) in each layer is mutuallydifferent, and the value of Re(550) in the layer having the smallervalue of Re(450)/Re(550) is larger than the value of Re(550) in thelayer having the larger value of Re(450)/Re(550).
 12. A retardationplate according to claim 1, wherein, at wavelengths of λ=450 nm, 550 nmand 650 nm, the retardation Re(λ) and the wavelength λ satisfy thefollowing relation: 0.2≦Re(λ)/λ≦0.3
 13. A retardation plate according toclaim 1, wherein, at wavelengths of λ=450 nm, 550 nm and 650 nm, theretardation Re(λ) and the wavelength λ satisfy the following relation:0.4≦Re(λ)/λ≦0.6
 14. A retardation plate according to claim 1, whereinthe intrinsic double refraction values of the two or more materials arepositive, a Material A of the two or more materials is transported andstretched in an identical direction to the transport direction to form amachine direction-stretched film, and a Material B of the two or morematerials is transported and stretched in a perpendicular direction tothe transport direction to form a transverse direction-stretched film.15. A retardation plate according to claim 1, wherein the intrinsicdouble refraction values of the two or more materials are negative, aMaterial C of the two or more materials is transported and stretched inan identical direction to the transport direction to form a machinedirection-stretched film, and a Material D of the two or more materialsis transported and stretched in a perpendicular direction to thetransport direction to form a transverse direction-stretched film.
 16. Aretardation plate according to claim 1, wherein the intrinsic doublerefraction values of the two or more materials are positive andnegative, and the materials of the two or more materials are transportedand stretched in one of an identical direction and a perpendiculardirection to the transport direction to form a machinedirection-stretched film and a transverse direction-stretched film. 17.A ½ wave plate comprising: a laminate of a polarizing plate, and aretardation plate wherein, at λ=450 nm, 550 nm and 650 nm, theretardation Re(λ) and the wavelength λ satisfy the relation:0.4≦Re(λ)/λ≦0.6, and the polarizing plate transmission axis of thepolarizing plate and the slow axis of the retardation plate intersecteach other.
 18. A ½ wave plate according to claim 17, wherein thepolarizing plate transmission axis of the polarizing plate and the slowaxis of the retardation plate intersect each other at an angle of 30° to60°.
 19. A circularly polarizing plate comprising: a laminate of apolarizing plate, and a retardation plate wherein, at λ=450 nm, 550 nmand 650 nm, the retardation Re(λ) and the wavelength λ satisfy therelation: 0.2≦Re(λ)/λ≦0.3, and the polarizing plate transmission axis ofthe polarizing plate and the slow axis of the retardation plateintersect each other.
 20. A circularly polarizing plate according toclaim 19, wherein the polarizing plate transmission axis of thepolarizing plate and the slow axis of the retardation plate intersecteach other at an angle of 30° to 60°.
 21. A reflective liquid crystaldisplay comprising: a laminate of a reflector,a liquid crystal cell, anda polarizing plate laminated in this sequence,and a retardation plateformed by laminating two or more materials having different intrinsicdouble refraction values between the reflector and the polarizing plate,wherein the retardation plate satisfies the relation:Re(450)<Re(550)<Re(650), where Re(450), Re(550) and Re(650) areretardation values in wavelengths 450 nm, 550 nm and 650nm,respectively.
 22. A method of manufacturing a retardation platecomprising the steps of: transporting and stretching in an identicaldirection to the transport direction a Material A to form a machinedirection-stretched film, transporting and stretching in a perpendiculardirection to the transport direction a Material B to form a transversedirection-stretched film, and laminating the machine direction-stretchedfilm and the transverse direction-stretched film, wherein the Material Aand B have different positive intrinsic double refraction values, andthe retardation plate comprises: a laminate of two or more materialshaving different intrinsic double refraction values, wherein theretardation plate satisfies the relation: Re(450)<Re(550)<Re(650), whereRe(450), Re(550) and Re(650) are retardation values in wavelengths 450nm, 550 nm and 650 nm, respectively.
 23. A method of manufacturing aretardation plate according to claim 22, wherein the step of laminatingis one of (1) a lamination step performed by transporting stretchedfilms together in an identical direction, (2) a lamination stepperformed by sticking wherein the slow axes in the stretched films arearranged to be perpendicular, and (3) a lamination step performed bysticking using an adhesive.
 24. A method of manufacturing a retardationplate according to claim 22, wherein the step of forming the machinedirection-stretched film,the step of forming the transversedirection-stretched film, and the step of laminating, are performedcontinuously.
 25. A method of manufacturing a retardation platecomprising the steps of: transporting and stretching in an identicaldirection to the transport direction a Material C to form a machinedirection-stretched film, transporting and stretching in a perpendiculardirection to the transport direction a Material D to form a transversedirection-stretched film, and laminating the machine direction-stretchedfilm and the transverse direction-stretched film, wherein the Material Cand D have different positive intrinsic double refraction values, andthe retardation plate comprises: a laminate of two or more materialshaving different intrinsic double refraction values, wherein theretardation plate satisfies the relation: Re(450)<Re(550)<Re(650), whereRe(450), Re(550) and Re(650) are retardation values in wavelengths 450nm, 550 nm and 650 nm, respectively.
 26. A method of manufacturing aretardation plate according to claim 25, wherein the step of laminatingis one of (1) a lamination step performed by transporting stretchedfilms together in an identical direction, (2) a lamination stepperformed by sticking wherein the slow axes in the stretched films arearranged to be perpendicular, and (3) a lamination step performed bysticking using an adhesive.
 27. A method of manufacturing a retardationplate according to claim 25, wherein the step of forming the machinedirection-stretched film,the step of forming the transversedirection-stretched film, and the step of laminating, are performedcontinuously.
 28. A method of manufacturing a retardation platecomprising the steps of: transporting and stretching in one of anidentical direction and a perpendicular direction to the transportdirection, two or more materials having positive and negative intrinsicdouble refraction values to form one of a machine direction-stretchedfilm and a transverse direction-stretched film, and laminating thestretched films, wherein the retardation plate comprises: a laminate oftwo or more materials having different intrinsic double refractionvalues, wherein the retardation plate satisfies the relationRe(450)<Re(550)<Re(650), where Re(450), Re(550) and Re(650) areretardation values in wavelengths 450 nm, 550 nm and 650 nm,respectively.
 29. A method of manufacturing a retardation plateaccording to claim 28, wherein the step of laminating is one of (1) alamination step performed by transporting stretched films together in anidentical direction, (2) a lamination step performed by sticking whereinthe slow axes in the stretched films are arranged to be perpendicular,and (3) a lamination step performed by sticking using an adhesive.
 30. Amethod of manufacturing a retardation plate according to claim 28,wherein the step of forming the stretched film, and the step oflaminating, are performed continuously.